1. Field of the Invention
The present invention relates to video input and output devices.
2. Description of the Related Art
Pixels are the fundamental unit upon which all displays function. Short for Picture Element, a pixel is a single point in a graphic image. Graphics monitors display pictures by dividing the display screen into thousands (or millions) of pixels, arranged in rows and columns. The pixels are so close together that they appear connected.
The quality of a display system largely depends on its resolution, how many pixels it can display, and how many bits are used to represent each pixel. VGA systems display 640 by 480, or 307,200 pixels. In contrast, SVGA systems display 800 by 600, or 480,000 pixels.
The number of bits used to represent each pixel determines how many colors or shades of gray can be displayed. For example, in 8-bit color mode, the color monitor uses 8 bits for each pixel, making it possible to display 2 to the 8th power (256) different colors or shades of gray. True Color systems use 24 bits per pixel, allowing them to display more than 16 million different colors.
Different types of display technologies use different methods to isolate pixels. For example, cathode ray tube (CRT) monitors work by aiming a beam of electrons at some phosphor, which in turn glows. This glow is perceived as a pixel on the screen. A standard color monitor has one red, one green and one blue dot at each location on the screen. A corresponding electron gun for each color emits an electron beam of varying intensity, which corresponds to color brightness.
To ensure that the electrons from each gun strike the corresponding phosphor, a shadow mask can be used. FIG. 1A depicts an exemplary conventional shadow mask 100. Because the three electron beams arrive at slightly different angles (from the three separate electron guns), it is possible to construct and align the shadow mask 100 such that the electron beam from one gun will strike the correct phosphor dot, but the other two phosphors will be in shadow. The intensity of red, green and blue can therefore be separately controlled at each dot triad location.
Some CRTs use an aperture grill instead of a shadow mask. FIG. 1B depicts an exemplary conventional aperture grill 150. The aperture grill 150 uses hundreds of fine metal strips that run vertically from the top of the screen surface to the bottom. These strips perform the same function as the shadow mask—they force the electron beam to illuminate only the correct parts of the screen.
Other systems, such as the Pioneer deep encased cell structure, available in plasma high-definition television (HDTV) displays from the Pioneer Corporation based in Tokyo, Japan, use three individual wells (one for each color element) for each pixel. FIG. 1C depicts an exemplary conventional deep encased cell structure 175. The deep encased cell structure 175 additionally includes black strips 180 run the length of the display to improve contrast. The black strips 180 are provided over deep black wells. The black strips 180 and the counterpart deep black wells can improve contrast in a display.
Displays can then be combined with digital cameras in order to facilitate two-way communication. Typically, a small digital camera is placed in close proximity to a display. FIG. 2 shows an exemplary conventional two-way communication set-up 200. A digital camera 210 is mounted on top of a computer monitor 205 in order to capture the facial expressions of the user. Digital images are generally captured with an integrated circuit having a charge-coupled devices (CCD) and/or complementary metal-oxide-semiconductor CMOS imagers. CCDs and CMOS imagers are specially made integrated circuits that respond to light. CCDs and CMOS imagers are used to capture image data in devices such as telescopes, bar code readers, digital still and video cameras, and scanners. A CCD is a collection of tiny light-sensitive diodes, which convert photons (light) into electrons (electrical charge). These diodes are called photosites. Each photosite is sensitive to light—the brighter the light that hits a single photosite, the greater the electrical charge that will accumulate at that site.
Although the described technologies work well in many applications, there are continuing efforts to further improve user experience.